1. Field Of The Invention
The present invention is directed to screens; to filtering screens; to devices with vibrating screens; to shale shakers with vibrating screens; to shale shakers with screens in series and with tiered screens; and to methods and devices for sealing screen interfaces and for aligning adjacent screens.
2. Description of Related Art
The prior art discloses a wide variety of vibrating screens, devices which use screens, shale shakers, and screens for shale shakers. In shale shakers which use a plurality of screens, problems are encountered with the leakage of drilling fluid, e.g. mud, between screens.
Drilling fluid, e.g. mud, typically a mixture of clay and water and various additives, is pumped through a hollow drill string (pipe, drill collar, bit, etc.) down into a well and exits through holes in a drillbit. The mud picks up cuttings (rock chips) and other solids from the well and carries them upwardly away from the bit and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is introduced to a shale shaker, a device which typically has a series of screens disposed end-to-end and arranged in tiered or flat disposition with respect to each other. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create viscosity and gel problems in the mud, as well as increasing wear in mud pumps and other mechanical equipment used for drilling. In some shale shakers a fine screen cloth is used with the vibrating screen. The screen may have two or more overlying layers of screen cloth. The frame of the vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism, e.g. unbalanced weights on a rotating shaft connected to the frame. Each screen may be vibrated by vibratory equipment to create a flow of trapped solids on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed.
Many screens used with shale shakers are flat or nearly flat (i.e. substantially two-dimensional). Other screens, due to corrugated, depressed, or raised surfaces are three-dimensional. Such screens present problems of alignment, continuity, and sealing when two or more of them are used adjacent each other in series. When such screens are also tiered the problems are exacerbated. Simply butting the screens up against each other is not an adequate solution, nor is spacing them apart leaving a trough between screen ends. There has long been a need for efficient devices and apparatuses for effectively utilizing a series of two- or three-dimensional screens.